Silver nanowires display potential as ITO replacement

19 May 2016

"The fact we are able to produce devices using similar methods as currently in use, but in a less energy-intensive way is an exciting step towards flexible gadgets that do not just open the door for new applications, but do so in a much greener way."Alan Dalton, University of Surrey

Research recently published in Materials Today Communications and Scientific Reports describes how silver nanowires are proving to be the ideal material for flexible, touch-screen technologies, while also exploring how the material can be manipulated to tune its performance for other applications. Currently, touchscreen displays mainly rely on electrodes made from indium tin oxide (ITO), a material that is expensive to source and process, and very brittle.

A team from the University of Surrey in the UK, led by Alan Dalton, in collaboration with M-SOLV, a touch-sensor manufacturer based in Oxford, were looking for alternative materials to overcome the challenges of ITO, which can be difficult to obtain at the moment. Alternative materials investigated as ITO replacements have included graphene, carbon nanotubes and random metal nanowire films. This study now indicates that films made up of an interconnected network of silver nanowires could be the strongest candidate, as such films possess transmittances and conductivities that can match and readily exceed those of ITO.

Matthew Large, first author of the paper in Scientific Reports, described the importance of these latest findings. "Our research hasn't just identified silver nanowires as a viable replacement touchscreen material, but has gone one step further in showing how a process called 'ultrasonication' can allow us to tailor performance capabilities," he explained. "By applying high frequency sound energy to the material we can manipulate how long the nanosized 'rods' of silver are. This allows us to tune how transparent or how conductive our films are, which is vital for optimizing these materials for future technologies like flexible solar cells and roll-able electronic displays."

In a paper recently published in Materials Today Communications, the same team showed how silver nanowires can be processed using the same laser ablation technique commonly used to manufacture ITO devices. Using this technique, the team produced a fully operating five-inch multi-touch sensor, identical to those typically used in smartphone displays, which performed similarly to one based on ITO but required significantly less energy to produce.

"Not only does this flexible material perform very well, we have shown that it is a viable alternative to ITO in practical devices," concluded Dalton. "The fact we are able to produce devices using similar methods as currently in use, but in a less energy-intensive way is an exciting step towards flexible gadgets that do not just open the door for new applications, but do so in a much greener way."

"We are seeing a lot of interest from our customers in silver nanowire films as an ITO replacement in devices," said Maria Cann, a technologist from M-SOLV and first author of the Materials Today Communications paper. "This work is a really important step in establishing exactly which sensor designs can make good nanowire products. The fact that the nanowire films are processed by the same laser techniques as ITO makes the transition from ITO to nanowires really straightforward. It won't be long before we are all using nanowires in our electronic devices."

The team, now based at the University of Sussex, is currently looking to improve the scalability of the process to make it more industrially viable. One limiting factor is the current cost of silver nanowires. Funded by Innovate UK and the UK Engineering and Physical Sciences Research Council (EPSRC), the team are collaborating with M-SOLV and a graphene supplier, Thomas Swan, on using electrodes made from a combination of nanowires and graphene to markedly reduce the cost.

This story is adapted from material from the University of Surrey, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.

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